Self-starting synchronous electric motor



N6v. 5, 1935..- w. KOHLHAGEN 2,019,583

SELF STARTING SYNCHRONOUS ELECTRIC MOTOR Filed April 4, 1934' 2 Sheets-Sheetl Nov. 5, 1935. w. KOHLHAGEN 2,019,683- saw snnwme sviwnnonous ELECTRIC uo'ron Filed April 4, 1934 2 Sheets-Sheet 2 Patented Nov. 5, 1935 UNITED STATES SELF-STARTING SYNCHBONOUS ELECTRIC MOTOR Walter Kohlhagen, Waterbury, Conn. Application April 4, 1934, Serial No. 718,891 6 Claims. (0!. 172-278) This invention relates to an improvement in synchronous electric motors and particularly to self-starting synchronous electric motors primarily designed for-use in connection with clocks atnd other time instruments, though not so lim- 1 ed.

Self starting' synchronous electric motors, when constructed so as to have suflicient selfstarting torque under various operating conditions, are prone to jump to a speed above their intended synchronous speed, with the result that they fail to discharge their proper time functions.-

One of the objects of the present invention is to provide a superior self-starting synchronous electric motor, which while having ample self: starting torque, nevertheless is substantially .prooi' against Jumping to super-synchronom Speeds sidered in conjunction with torque at relatively-low synchronous under operating conditions, such, for instance, as when subjected to a varying load, as in a strike clock.

A further object is to provide a self-starting synchronous electric motor having superior speed.-

Another object is to starting synchronous electric motor which may be relied upon to start, from rest and accelerate to synchronous speed despite appreciable loads, when connected to a source of current of proper voltage and frequency.

Other objects and advantages will appear to those skilled in the'art from the following, condrawings and the appended claims.

. In the accompanying drawings:

Fig. l is a face view of one form which a selfstarting synchronous electric motor may assume in accordance with the present invention;

Fig. 2 is a top edge view thereof;

mg. 3 is a'vertlcal sectional view taken on the line 3-4 of Fig. 2; i

Fig. 4 is a broken fragmentary sectional view takenonthelinel-lofFig.1;

Fig. 5 is a schematic perspective view showing the parts in extended positions; and 3' 8. 6 is a perspective view p'artiyin section of the rotor-unit, detached..

The particular self-starting us electric motor herein chosen as illustrative of the present invention includes a eompoimd stator structure having a pair of complementary polepieces II and of iron or other suitable mag netie material, which for convenience of description may be referred to as "primary" pole-pieces, and a pair of complementary pole-pieces i2 and I2 ofiron'orthelike which'maybe designatedas provide a superior selfthe accompanying "second'ary pole-pieces. The lower ends of the primary pole-pieces I II and II are interconnected by a laminated core-piece l4 mounting theusual electromagnet coil i5, while the secondary polepieces l2 and I I are free of such interconnection, v for reasons as will hereinafter appear The primary pole-pieces ill and II and the secondary pole-pieces l2 and I: are laterally spaced from each other by spacing-bushings l6 sleeved over the reduced rear ends ll of studs l8 riveted 1 to and rearwardly-ofisetting from a mountingplate I9. Suitable nuts such 2|], one of which is applied to the threaded rear end of each of the studs ll, serve to retain the pole-pieces l2-l3, the spacing-bushings l6 and the pole- 15 pieces ill-ll in place.

Preferably, the bushings l6, studs l8 and plate It are formed of brass or other non-magnetic material, so as to minimize magnetic leakage. The primary pole-piece III is formed with two so salient-poles 2| and 22 respectively having their inner faces curved to substantially conform to the peripheral curvature of acup-shaped rotormember 23 of magnetic material and having a laterally-extending flange 24 which is notched 25 to produce an annular series of equidistant salient-poles 25 magnetically acted upon by the salient-poles 22 of the primary pole-piece Ill before referred to. As shown, the salient-pole 2| has sleeved over it a plurality of washer-like shadso ing-coils 26 serving to cause a time-lag of the ,magnetic flux in the manner common to splitphase electric motors.

The primary pole-piece ll compiementingthe primary pole-piece II, and located on the opas posite side of the cup-shaped rotor-member 23 therefrom, is provided with salient-poles 21 and 22 having their concave inner faces located close- Lv adjacent the periphery of the cup-shaped rotor-member 23. Each of the said salient-poles 4o 21 and 28 is notohedto create spaced polarterminals 28 and II and the latter salient-pole is provided with a plurality of disk-like shadingcoilsllservingtodisplacethefluxpassing through the said salient-pole 20 as compared Q to that through the said salient-pole 21. As thus'constructed and arranged. the primary pole-pieces II and magnetically act upon the rotor-member 22 with a. rotating-field eifeet to the'said rotor-member in the direction indimemberaandthespacingofthepolar-terminals some ",theturningeiiectriaf to synchronmLe.,eflecting-theturningofthe rotor-member said rotor-member at a speed of 600 R. P. M. with 60-cycle current in the particular motor-structure herein illustrated.

The cup-shaped rotor-member 2| before described is mounted upon a collet 82 preferably of brass or similar material, and the latter in turn is staked upon a rotor-shaft a turning in a hearing-bushing 34 mounted with a drive-fit in the mounting-plate i9, and rearwardly offsetting therefrom and projecting slightly forwardly therethrough. At its forward end, the rotorshaft 33 is provided with a pinion 35 by means of which the power of the motor may be taken on to drive a clock mechanism or the like.

The rear end of the said rotor-shaft II has staked to it a collet Ii of brass or similar material which in turn has secured to it a disk-like rotor-member 31 of'permanent magnet material,

such as glass-hard steel, and formed in its face adjacent its periphery with an annular stiiiening-rib or bead 38.

The rotor-member 31 is free or substantially free of salient-poles and acts, for the purpose as will hereinafter appear, polar spots impressed upon it adjacent its periphery (as indicated by broken lines in Figs. 1 and and retained thereon with appreciable resistance to change or displacement by virtue of its permanent nated for convenience of description as the hysteresis" rotor-member and is located in line with the secondary pole-pieces l2 and i3, so as to be magnetically acted upon by the same. The said secondary pole-pieces l2 and ii are of corresponding and interchangeable form and size, and each is provided with three (more or less) salientpoles 39, 40 and M projecting to a position closely adjacent the periphery of the hysteresis rotormember before referred to.

By reference to Figs; 1 and 5, it will be seen that the salient-poles 39, 40 and II of a given one of the secondary pole pieces l2 and I! are spaced from each other a distance equivalent to the space between two polar spots of like polarity on the hysteresis rotor-member 31, so that the said rotates one-twelfth turn for each one-half cycle, rather than double that speed, be the case were the intermediate salient-poles ll of opposite polarity from the polarity of their companion salient-poles 39 and H.

The secondary pole-pieces l2 and I: in the construction-herein chosen for illustration are magnetized solely by stray magnetic flux from the coil l5 and the primary pole-pieces ill and l l, but by virtue of this stray flux these pole-pieces and their salient-palm 38, 40 and II exert sum; cient synchronous torque upon the hysteresis ro-" tor-member 31 to confine the speed thereof and hence the speed of the entire rotor-unit, comprising the parts 24, 33 and 31, to a synchronous speed of 600 R. P. M.

Under certain conditions, if desired, the secand It may be magnetilation, so to speak, of the said secondary polepieces I! and I8 is preferable instructures having the proportions of that shown in the accompanying drawings. As will be apparent from the foregoing, the salient-poles 39, II and 4| (which appropriately may be designated as salient-poles) produce a stationary-axis alternatmember 31 by its capacity for having ing-fleld owing to the absence of shading ils therefrom, in contmdistinction to the rota field eil'ect produced by the primary salient-poles II, 22, 21 and 28 before referred to.

When current of the proper voltage and fre- 5 quencyjs supplied to the coil I I, the primary salient-poles Ii, 22, 21 and 28 will exert a turning effect upon the rotor-member 23 and bring the same up to synchronous speed, which in the structure illustrated with a 60-cycle current, would be 600 R. P. M. Simultaneously with the creation of the rotating magnetic field as just described, a stationary-axis alternating-field will be created by the secondary salient-poles 39, ll and ll of the respective secondary pole-pieces I 2 and II, but the interlocking tendency between the said salient-poles and the hysteresis rotorwill be insuiiicient to materially retard the speeding-up of the rotor-unit; (comprising the members 24, 33 and 31) to the synchronous speed as above described. The ing eiIect of the secondary salient-poles 39, 40 and II upon the rotor-member 31, once synchronous speed is reached, will be suflicient to eifectively prevent the over-speeding of the entire rotorat unit under practically all operating conditions, such, for instance, as in a strike clock when the motor structure might be subjected to sudden changes in leads.

The invention may be carried out in other specific ways than that herein set forth without departing from the spirit and essential characteristics of the invention; and the present embodiment is, therefore, to be considered in all respects as illustrative and not restrictive, and all changes 35 coming within the meaning and equivalency range of the appended claims are intended to be embraced therein,

I claim:

l. A self-starting synchronous electric motor 40 device including in combination a rotor-unit havlog a. portion provided withsalient-poles and a sis portion of permanent magnet material substantially free of salient-poles and having remanent polar-spots thereon; and a stator structure having primary salient-poles produc- 0 ing a starting and a synchronous effect upon the portion of the said rotor having salient-poles, the said stator structure also having secondary salient-poles producing a stationary-axis alterhating-field effect upon the hysteresis portion of the said rotor-unit which is substantially free of salient-poles; the said secondary salient-poles being arranged with pole: of the same instantaneous polarity adjacent and acting on said rotor-unit to restrain the same from super-synchronous speed.

3. A self-starting synchronous electric motor device including in combination a rotor-unit havpermanent-magnet 55 nent magnet material substantially free or salient-poles and having remanent polar-spots thereon; and a stator structure having primary salient-poles producing a starting and a synchronous eiiect upon theportion oi the said rotor having salient-poles, the said stator structure also having secondary salient-poles producing a stationary-axis alternating-field eiiectupon the permanent-magnet hysteresis portion 0!, the said rotor-unit which is substantially free of salient-poles.

4. A self-starting synchronous electric motor device including in combination a rotor-unit having a portion provided with salient-poles and a hysteresis portion or permanent magnet material substantially tree of salient-poles and having remanent polar-spots thereon; and a statorstructure havingprimary salient-poles producing a starting and a synchronous eflect upon the portion of the said rotor-unit having salient-poles. the said stator structure also having a pair of complementary secondary pole-pieces, each provided with a plurality of secondary salient-poles producing a stationary-axis alternating-field eftect upon the permanent-magnet'hysterasis portion of the said rotor-unit which is substantially tree of salient-poles; the said secondary salientpoles of each secondary pole-piece being spaced apart a distance equivalent tothe-normal distance between two polar-spots on the adjacent hysteresis portion 0! the said rotor-unit.

6. A compound self-starting synchronous-mo- .tordevioe,inciudingincombination: ailrstset 3 oi stator-poles producing a rotating-field mm a second set at stat'obpoles producing a substantially-stationary-axis alternating-field eiiect: a

- iirst rotor-portion cooperating with the said first set'ot stator-poles and providing both self-start- 5 salient poles and having r'emanent polar spots impressed therein of regularly-alternating polarity under normal operating conditions; and a so stator structure having means exerting a starting and synchronizing eilect upon the said primary rotor member and also having means producing a synchronizing eflect uponthe said secondary rotor memberincluding salient poles at spaced apart a distance at least equal to the distance between two spots of like polarity on the said secondary rotor member and acting in conjunction with the polar spots on the latter rotor member to restrain the said primary rotor memso her from super-synchronous speed. 

